On the Leading Edge: Improving Artificial Joint Performance

Dartmouth-Hitchcock

October 12, 2012

With the baby boomer generation coming to a "certain age," Dr. Stephen Kantor and his colleagues within Dartmouth-Hitchcock's highly-regarded orthopedic program are seeing many more patients from their late 40s to early 60s who are facing the dilemma of having osteoarthritis but who want to maintain their active lifestyles...

World-Class Research

That makes research conducted by leading academic centers such as D-H all the more vital. For example, Kantor and his joint team partner, Dr. Ivan Tomek, have led a number of national studies to evaluate the safety and effectiveness of new implant designs. D-H surgical teams also have the unique benefit of being able to meet regularly with one of the world's foremost authorities on why artificial joints fail – Dr. Michael Mayor, who has been serving on an FDA advisory panel in Washington, DC that is reviewing the ASR case.

Mayor, who led a highly distinguished, 40-year career as an orthopedic surgeon at D-H, has also worked with metallurgical engineer John Collier, PhD, and other experts over the years at Dartmouth's Thayer School of Engineering to develop biomedical materials and techniques that have become industry standards for improving artificial joint performance. Their efforts have included reaching out to the international orthopedic community, inviting surgeons to send their explanted, failed implants to Dartmouth for analysis.

Many have answered the call. Over the years, [The Dartmouth Biomedical Engineering Center] has compiled the world's largest collection of retrievable implants, more than 12,000 to date (including all metal-on-metal models currently in the marketplace). "Some of them are stored in our lab," he says, "but the collection is so large now we've actually had to rent storage space in a warehouse. We do a rigorous analysis of each one that includes photography, computer-generated imaging, and other assessments such as those involving metallurgy and polymer science, as needed. We then generate a comprehensive report to send back to the surgeon."

The Right Stuff

As increased patient demand has prompted manufacturers to come up with more innovative designs to improve wear performance, more all-metal and all-ceramic implants have been introduced to the market. "They've worked well in the majority of patients, but some models like the ASR have been more vulnerable to breakdown," explains Mayor. "Though the surfaces are highly-polished – which proponents have thought would make them wear better and which looked good in simulator tests – these surfaces tend to wear down and generate debris, causing the implant to fail early."

"We've been able to establish, in a large 10-year follow up study, that a combination of soft and hard materials – a polyethylene socket with a metal or ceramic ball – has performed extremely well, with almost no complications and a 98 percent successful durability in patients," he says.

Not surprisingly, that is the choice of Kantor and his surgical colleagues at D-H.

"I feel very fortunate to be part of an academic health system where research is one of our missions, and where we have access to a wonderful resource like Dr. Mike Mayor and our other colleagues at Thayer. The knowledge we've gained from our research efforts has proved invaluable – both in understanding which implant designs can provide optimal wear performance, and in helping patients select the implant that will best meet their needs."